The present invention relates to a magnetic head drum of a helical-scan type for magnetically recording and reading video data on a magnetic tape.
Such a magnetic head drum known in the art comprises a stationary spindle, a stationary drum secured to the spindle, a rotary drum rotatably supported on the spindle by bearings, and a motor for rotating the rotary drum. The stationary drum has a cylindrical side wall formed on its outer circumferential face with a helical guide shoulder for helically guiding a magnetic tape thereon. The rotary drum also has a cylindrical side wall which is disposed in circumferentially aligned relationship with the stationary drum and provided at its outer periphery with a magnetic head for recording and reading video signals on the magnetic tape. At an inner circumferential face of the cylindrical side wall of the rotary drum is provided a damping yoke made of a laminated plate including steel films and a resin layer interposed therebetween. The motor comprises a rotor secured to the rotary drum and a stator secured to the spindle being remote at a predetermined distance from the rotor. The stationary drum also is provided with a transformer for the stator which is arranged so as to be opposed to a transformer for the rotor disposed on the rotor side. Further, the stator is provided, at its circumferential edge, with a cylindrical damper in order to restrain vibration of the stator upon rotation of the rotary drum. The vibration causes a noise, viz, electromagnetic noise of the motor.
However, upon rotation of the rotary drum, neither the damping yoke nor the stator with the damper is effectively released from the vibration. As a result, the electromagnetic noise is still generated.
There is a great demand for a magnetic head drum rotatable at high speed without generating the electromagnetic noise and suitable for an apparatus such as a digital video tape recorder.